Detection of urinary Vi antigen as a diagnostic test for typhoid fever

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Abstract
In Santiago, Chile, the results of the slide coagglutination method and enzyme-linked immunosorbent assay [ELISA] for detection of Vi antigen in urine of patients with acute typhoid fever, paratyphoid fever and other febrile illnesses and in afebrile control subjects were compared. Using a cut-off value that maximally separated typhoid patients from controls, the ELISA was positive in 62.4% of 141 patients with culture-proven typhoid infections and in 13.2% of 159 afebrile control subjects. ELISA was false positive in 64.7% of 34 culture-proven paratyphoid A or B patients and 47.1% of 21 patients with other nontyphoidal febrile illnesses. The coagglutination test was positive in 34% of typhoid patients, 14% of afebrile control subjects and 46% of febrile control subjects. Thus, these tests, when performed with the Vi antibodies employed in this study, are of little value for the diagnosis of typhoid fever in this setting.